Separator device for a system for recirculation of the blow-by gases of an internal combustion engine

ABSTRACT

A separator device for a system for recirculation of the blow-by gases of an internal combustion engine includes a casing containing a separation chamber and having an inlet for communication with the engine crankcase and an outlet for communication with the engine intake manifold, and drainage outlets ending in the engine crankcase, for returning the liquid separated in the separation chamber into the engine crankcase. Actuator means sensitive to pressure in the engine crankcase are associated to the inlet and to the drainage outlets so that when the pressure in the engine crankcase is higher than the pressure in the separator device, the inlet is open and the drainage outlets are closed, while when the pressure in the engine crankcase is lower than the pressure in the separator device, the inlet is closed and the drainage outlets are open.

The present invention refers to separator devices used in recirculationsystems for blow-by gases of internal combustion engines, of the typecomprising a casing containing a separation chamber and having an inletfor communication with the engine crankcase, a main outlet forcommunication with the engine intake system and one or more drainageoutlets ending in the engine crankcase for discharging the separatedliquid into the separation chamber.

In the internal combustion engines, after having separated and returnedthe oil mixed thereto to the engine crankcase in form of vapour and/ordroplets, the blow-by gases leak through the clearance between thepistons and engine cylinders, passing from the cylinders to the enginecrankcase, are recirculated to the engine intake. Therefore, the task ofthe separator device is that of allowing the recirculation of theblow-by gases, in the system for supplying air, to the engine,simultaneously preventing the liquid particles from ending up in theintake.

In engines with three or more cylinders, except for particular cases,the pressure in the engine crankcase is almost constant over a rotationof the engine shaft. As a matter of fact, the balance between theupwards and downwards strokes of the various pistons is such that theengine crankcase maintains the volume thereof almost unvaried during theoperation. In particular, regarding the four in-line cylinders engines,the volume of the engine crankcase remains substantially constant, inthat while two pistons move towards the top dead centre the other twopistons move towards the bottom dead centre.

In such engines, a pressure regulation valve (PRV) of the diaphragm andspring type or a nozzle with cross-section variable by means of ashutter (PCV: Positive Crankcase Ventilation Valve) are used with theaim of maintaining the engine crankcase under vacuum at any operatingcondition. Such valves are used to provide communication between theengine crankcase and an environment subjected to vacuum, typically theengine intake manifold; possibly, a further connection with the intakesystem, regulated by a valve, so as to generate a fresh airflow fromoutside the crankcase (positive crankcase ventilation) may also beprovided with the aim of reducing the level of contamination of the oiland increase duration thereof. Such valves are capable of correctlyperforming their task in that the instantaneous pressure in the enginecrankcase is scarcely variable. Obviously, when the intake systemgenerates insufficient vacuum (high loads and/or supercharge conditions)the engine crankcase cannot be maintained under vacuum.

In the in-line two cylinder engines with 360° offset of the enginecycles (i.e. of the type where the two pistons move in the samedirection, so that they move together towards the top dead centre andtowards the bottom dead centre), as well as in the single cylinderengines, the instantaneous pressure in the engine crankcase issignificantly variable, due to the considerable variation of the volumeof the engine crankcase within a rotation of the engine shaft connectedto the motion of the pistons in the same direction. In this case, theuse of valves of the previously described type does not allow obtaininga correct regulation of the pressure. With engines of this type, eventhe liquid/gas separation is complex, due to the reciprocating motion ofthis mixture in the separator. In the three or four cylinder engines themotion of the mixture may be intermittent but not reciprocal.

Systems of the type indicated in the preamble of claim 1 are known fromEP 2 146 061 A1, US 2004/261776 A1, DE 20 2005 009990 U1.

SUMMARY OF THE INVENTION

The object of the present invention is that of providing a separatordevice useable with advantage particularly with in-line two-cylinderengines with zero degree offset cranks or in single-cylinder engines,with the aim of obtaining an ideal separation action, an efficientdrainage of oil towards the engine crankcase and maintaining the enginecrankcase under vacuum at any operating condition, regardless of theavailability of an environment under vacuum.

According to the invention, such object is attained due to the fact thata separator device is provided having the characteristics indicated inclaim 1.

Due to such solution, in the application of the device according to theinvention to an in-line two cylinder engine with pistons moving in thesame direction, when the pistons move towards the bottom dead centre, soas to reduce the volume in the engine crankcase and increase thepressure therein, the actuator means associated to the inlet of theseparator device open and allow the entry of the gas and liquid mixtureinto the separator device. Under such condition, the actuator meansassociated to the drainage outlets are closed. When the direction ofmotion of the pistons is inverted and the pressure in the enginecrankcase reduces, the actuator means on the inlet of the separatordevice close, while the actuator means associated to the drainageoutlets open. Thus, the oil separated in the separator device may returninto the engine crankcase.

In such step, the vacuum in the engine crankcase creates an airflowcoming from the engine intake through the outlet of the separatordevice, the internal chamber of the separator device and theabovementioned drainage outlets. Such airflow has the purpose ofdraining the separated liquid and cleaning the engine crankcase, thuscontributing to reduce the contamination of oil by the blow-by gases.Therefore, with the device according to the invention it is possible toobtain a positive crankcase ventilation), without using a PRV valve orthe like.

Furthermore, according to a further characteristic of the invention, theentire section for passage through the drainage outlets of the separatordevice is much smaller than the section for passage to the inlet of theseparator device. Thus, the negative half wave of the pressure cycle inthe engine crankcase has a larger area with respect to the positive halfwave and the average pressure in the engine crankcase is consequentlynegative. Generally, the size of the drainage passages has an impact onthe vacuum level generated in the engine crankcase.

The present invention has the object of providing both the separatordevice independently and an internal combustion engine using theseparator device of the invention, particularly a single cylinder engineor an in-line two cylinder engine with pistons moving in the samedirection.

BRIEF DESCRIPTION OF THE DRAWINGS

Further characteristics and advantages of the invention shall beapparent from the description that follows referring to the attacheddrawings, provided purely by way of non-limiting example, wherein:

FIG. 1 is a perspective view of an embodiment of the separator deviceaccording to the invention,

FIG. 2 is a sectional schematic view of the separator device of FIG. 1,

FIG. 3 is an enlarged scale perspective view of a detail of FIG. 1,

FIG. 4 is a sectional view of the detail of FIG. 3,

FIG. 5 is a perspective view of a further detail of FIG. 1,

FIG. 6 is a bottom view of one of the drainage outlets of the separatordevice,

FIG. 7 is an enlarged scale sectional view of the detail of FIG. 5,

FIG. 8 is a diagram illustrating the variation cycle of the pressure inthe engine crankcase of the engine according to the invention, and

FIGS. 9, 10 are schematic views of the separator device according to theinvention showing the two different steps of the operative cycles of thedevice according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, number 1 indicates in its entirety, a separatordevice used in a system for the recirculation of the blow-by gases of aninternal combustion engine. The illustrated example specifically refersto the case of an in-line two cylinder engine with cranks offset by 0°,i.e. with pistons moving in the same direction towards the top deadcentre and towards the bottom dead centre. The separator device 1 has acasing 2 defining a separation chamber 3 therein (FIG. 2) and having aninlet 4 communicating with the environment of the engine crankcase, anoutlet 5 connected to the engine intake manifold or in any case to theengine air intake system and any number of outlets 6 for draining theoil separated in the chamber 3, ending in a cavity of the enginecrankcase (two outlets 6 are provided in the illustrated example).

As observable in detail in FIG. 4, a leaf shutter 7 is providedconstituted by at least one flexible metal leaf—anchored to the casing 2of the device at 8—which is maintained adhering to a wall 2 a in whichthe opening constituting the inlet 4 when the engine crankcase is undervacuum is provided, while it bends allowing the entry of the blow-bygases and vapours mixture and oil droplets into the separator 2 when thepressure in the engine crankcase is higher than the pressure value inthe separator device 2 at the inlet 4.

Still referring to FIGS. 2, 4, several partitions 9 defining a labyrinthpath are provided in the casing 2. A first partition immediatelyadjacent to the inlet 4, indicated with 10 in FIG. 4, is arranged andconfigured so that the mixture flowing into the separator device impactsthereagainst, facilitating separation.

The drainage outlets 6 are provided in form of cylindrical wellsarranged on the bottom of the casing 2 of the separator, each wellhaving a bottom wall 6 a whereon the olio separated in the separationchamber 3 is collected. The bottom wall 6 a has a plurality of passages6 b (see FIG. 6) which are controlled by a T-shaped shutter 6 c,schematically represented in the drawings (see FIG. 7 in particular).Each T-shaped shutter has a stem with a widened end fixed onto the bodyof the separator and a disc-shaped head constituting a flexible membranewhich is deformed opening and closing the passages 6 b varying thepressure in the engine crankcase.

In the present description and in the attached drawings the constructiondetails related to the flexible leaf 7 and the shutters 6 c are notshown, given that such details may be provided in any known manner andalso due to the fact the elimination of such details of the drawingsallows instant and easy understanding thereof.

FIG. 8 shows the variation cycle of the pressure in the engine crankcaseof an in-line two cylinder engine of the aforedescribed type, withpistons moving in the same direction, over time. As observable, theinstantaneous pressure in the engine crankcase considerably varies as afunction of the sensitive variation of the volume of the enginecrankcase over a rotation of the engine shaft, due to the movement ofthe pistons in the same direction. When the pistons move towards the topdead centre, the volume of the engine crankcase increases, hencecreating an environment under vacuum. On the contrary, when the twopistons move towards the bottom dead centre, the volume of the enginecrankcase reduces and the environment is subjected to pressure.

FIGS. 9, 10 show the two steps of the operative cycle of the deviceaccording to the invention. FIG. 9 refers to the step wherein thepressure in the engine crankcase is higher than the pressure in theseparator device. Under such condition, the leaf shutter 7 is open andthe T-shaped shutters 6 c are closed, the mixture follows the labyrinthpath from the inlet 4 to the outlet 5 so as to allow the separation ofolio and the return of the blow-by gases to the engine intake.

FIG. 10 refers to the step in which the pressure in the engine crankcaseis lower than the pressure in the separator device. In such step theleaf shutter 7 is closed and the T-shaped shutters 6 c open allowingdraining the oil separated in the chamber 3 in the engine crankcase. Insuch step, the vacuum present in the engine crankcase creates an airflowfrom the engine intake through the outlet 5, the chamber 3 of theseparator and the wells 6. As previously indicated, such airflow alsoserves the function of cleaning the engine crankcase, contributing toreduce the contamination of the oil by the blow-by gases and thusobtaining a positive crankcase ventilation without requiring a PRV valveor the like.

Still according to the invention, the entire section of passage throughthe holes 6 b associated to the wells 6 is however much smaller than theinlet passage 4 in the separator. Therefore, the negative half wave ofthe pressure cycle in the crankcase has a larger area with respect tothe positive half wave. Thus, the average pressure in the crankcase isnegative (see FIG. 8). Generally, the size of the drainage holes 6 c and6 b is selected so as to have a desired impact on the vacuum levelgenerated in the engine crankcase.

For the same reason, the motion of the mixture in the separator isprevalent towards the outlet. Furthermore, as observable from acomparison of FIG. 9 with FIG. 10, the return through the drainageoutlets 6 occurs along a different path with respect to that of thevapours in the step of FIG. 9 hence guaranteeing good separation in thestep illustrated in FIG. 9.

Naturally, without prejudice to the principle of the invention, thedetails and embodiments may vary, even significantly, with respect towhat has been described and illustrated strictly for exemplificationpurposes, without departing from the scope of the present invention.

1. A separator device for a system for recirculation of the blow-bygases of an internal combustion engine, comprising a casing containing aseparation chamber and having an inlet for communication with an enginecrankcase, an outlet for communication with an engine intake system andone or more drainage outlets ending in the engine crankcase fordischarging the separated liquid into the separation chamber, whereinrespective actuator means, sensitive to pressure in the enginecrankcase, are associated to said inlet and to said drainage outlets sothat when the pressure in the engine crankcase is higher than thepressure in the separator device the inlet is open and the drainageoutlets are closed, while when the pressure in the engine crankcase islower than the pressure in the separator device the inlet is closed andthe drainage outlets are open, wherein the actuator means associated tosaid inlet are constituted by a flexible leaf shutter, wherein saiddrainage outlets are in form of wells with a bottom wall in which theliquid separated in the separation chamber is collected, said bottomwall having passage holes and the respective actuator means comprising aT-shaped shutter suitable to obstruct said passage holes provided in thebottom wall of the wells, and several partitions defining a labyrinthpath provided within the casing, a first partition being immediatelyadjacent to the inlet and being arranged and configured so that themixture flowing through the inlet into the separator device impactsthereagainst, facilitating separation.
 2. Separator device according toclaim 1, wherein the entire area of the passage section defined by theabovementioned drainage outlets is smaller than the area of the sectionfor passage through said inlet.
 3. An internal combustion engine,comprising one cylinder or two cylinders having pistons movable in thesame direction towards the top dead center and towards the bottom deadcenter, so as to generate a pressure oscillation in the enginecrankcase, wherein said engine is provided with a separator deviceaccording to claim
 1. 4. An internal combustion engine, comprising onecylinder or two cylinders having pistons movable in the same directiontowards the top dead center and towards the bottom dead center, so as togenerate a pressure oscillation in the engine crankcase, wherein saidengine is provided with a separator device according to claim 2.